This application relates to an improved nozzle for applying a fluid to a surface to be cleaned. More particularly, this invention relates to such a nozzle in which a member is self-centering within the nozzle to create cavitation and apply a cavitating jet to efficiently and thoroughly clean the surface.
Modern cleaning systems often use a fluid jet to remove rust, scale or coatings from a surface to be cleaned. Typically, these surfaces are cleaned by the application of a fluid which carries an abrasive substance, such as sand. The use of a fluid carrying an abrasive is well known and commonly utilized to clean surfaces such as metal down to a bare metal surface. In many prior art systems, the use of a fluid without an abrasive material would not effectively clean the surface.
It is sometimes undesirable to use an abrasive carried in a fluid, since the abrasive may escape from the fluid and be mixed into the air surrounding the cleaning area. Further, the abrasive material may get into nearby machinery. Further, the abrasive material may contaminate environmental air and/or water. All these results are undesirable. For this reason, it is desirable to develop a cleaning system that utilizes a fluid jet which does not carry an abrasive material.
It is known in the prior art to utilize cavitation to increase the cleaning power of a fluid jet. Essentially, the principle of cavitation involves lowering the pressure of a fluid below its vapor pressure. As the fluid reaches pressures below the vapor pressure, bubbles of vaporized fluid form in the jet. As the jet strikes a surface to be cleaned, these bubbles implode and remove rust, scale or other coating. Cavitation may be undesirable in pumping fluids and for other fluid applications, however, it is beneficial in cleaning applications.
Problems exist with prior art nozzles which utilize cavitation since it is difficult to cause an adequate cavitation effect in a mass produced nozzle. It should be appreciated that in order for the nozzle to actually produce substantial cavitation bubbles, internal members must be accurately formed and positioned.
In some prior art devices, a pin member was received in the nozzle to lower the pressure of the fluid, thereby creating cavitation. It has been found that this pin member should be accurately positioned within the nozzle and centered along a nozzle center axis. Due to the relatively small sizes of the pins and nozzles which have been utilized, it is very difficult to center, and maintain the pins centered within the nozzles. This has resulted in the prior art cavitating nozzles being less efficient than desired.
In the prior art, the pin is typically secured within the nozzle bore by a thread connection. This provides insufficient accuracy in the axial position of the pin, which is an important variable in the efficiency of a cavitation nozzle. In addition, since these prior art pins were typically fixed relative to the nozzle, close attention was required during assembly to ensure that the pins were centered within the nozzle. Further, these fixed pins often moved off-center with use, which decreased the efficiency of the cavitating nozzles.
It is therefore an object of the present invention to provide a cavitating nozzle which receives a self-centering pin. It is further an object of the present invention to provide such a nozzle in which the pin is accurately positioned axially within the nozzle. It is further an object of the present invention to provide such a nozzle in which the axial position of the pin within the nozzle is less critical.